A leadframe is the metal frame a semiconductor is attached to during the package assembly process. In FIG. 1, an exemplary prior art leadframe 30 includes a die pad 36 on which a chip, or die, is eventually mounted. The corners of die pad 36 are attached to the leadframe's internal frame, or dam bar, 32, which supports the die pad 36. A plurality of leads 34 is also supported by the dam bar 32. The corners of the die pad 36 are connected to the dam bar 32 by a tie bar 38. The tie bars 38 have a down-set 40 so that die pad 36 is below the leads 34.
Discrete passive components, such as capacitors or inductors, currently are incorporated into electronic packages, such as integrated circuit (“IC”) packages, by attaching them to the substrate or leadframe of the packages. This causes the package size to increase, going against the trend of package minimization or miniaturization. A custom-designed leadframe for passive attachment is also required. The number of passive components, their size, and signal pair locations are also restricted using this approach.
When discrete passive components are attached onto leadframes with solder or conductive epoxy, the location of these components is very restricted. The land features for the attachment of these components are designed on the leads. The lead pitch (the distance from a centerline of one lead to a centerline of an adjacent lead) is often smaller than the size of the passive component and the component's possible locations are typically limited to the corner fan-out areas of the leadframe. Also, due to the “no-crossing” nature of leadframes, the land features are limited to adjacent pairs of leads. Since the size of the land features for attaching discrete passive components is limited by the spacing available on the leadframe, the physical size and location of the discrete passive components are also limited.
The attachment of wirebondable discrete passive components onto leadframes or the die is also problematic. Bond pads on the die are typically designed to accept one wirebond. However, to support wirebondable passive components, the bond pad has to be able to accept at least 2 bonds (one bond from the passive component to the bond pad, another bond to connect the bondpad to the package lead). In addition, there is a very limited supply source for wirebondable discrete passive components since not all passive components are available in wirebondable configuration; those that are available tend to have a high unit cost.
An additional problem is that the aluminum pads, to which components are often connected, offer limited connection options. Aluminum metal is not solderable and conductive epoxy cannot be used to attach discrete components to aluminum due to resultant high contact resistance. Typical aluminum wirebond pads are too small and too close together for attachment of even the smallest-sized discrete component.
Therefore, it would be advantageous to improve the manner in which discrete passive components are incorporated into electronic packages.